How to preselect the next tool after the current tool has been loaded

Each tool change necessitates an undesirable break in the automatic cycle of operation. In some machines, this break can be long. With machines equipped with a high quality automatic tool changer, the preselection of the current tool can be useful to reduce the time of these periodic interruptions. When the current tool is loaded into the machine spindle, the next tool is moved close to the machine spindle area for the next transfer.

CAM-POST provides built-in functionality to enable the post-processor to automatically preselect tools. Question #51 in the “Machine Description / Tool Change / Misc. Codes” section tells the post-processor when to preselect a tool if a SELECT/TOOL (or SELCTL) command is not present in the input NC program.

Answer “Immediately” to have CAM-POST output the preselection for the next tool immediately following the load operation of the current tool. Answer “Later” to defer the preselection of the next tool just before it is loaded. Answer “Both” to output the preselection twice: once immediately following the load of the current tool; and again just before the tool is actually loaded. This simplifies program restart.

CAM-POST can further speed up processing, by automatically preselecting the first tool to be used in the program after the last tool is loaded. This functionality is available via a Machine Shutdown RMD macro. RMD macros contain small fragments of macro code that perform specific actions. The “Ready first tool for restart” action makes sure that the first tool is selected before the program ends.

Benefit to User
The automatic selection of next tool after each tool change can both simplify NC programming and reduce non-cutting time in machining operations.

For more information or comments, please do not hesitate to contact Phil at